Effect Of Postoperative Radiotherapy In Women With Early Pure Mucinous Breast Cancer

PurposePure mucinous breast cancer(PMBC)is a specific subtype of breast cancer with favorable prognosis,in which the effect of postoperative radiotherapy has not yet been recognized.We aimed to investigate the prognostic value of postoperative radiotherapy in women with early-stage PMBC.MethodsIn this retrospective study,we selected women from the Surveillance,Epidemiology,and End Results(SEER)database diagnosed with first primary T1-2N0M0(tumor size?3cm)PMBC between 1998 and 2015.A total of 1076 eligible patients under the inclusion criteria were stratified into lumpectomy plus postoperative radiotherapy group,lumpectomy alone group and mastectomy alone group.Kaplan-Meier method and COX proportional hazards regression model were used to evaluate the effect of radiotherapy on breast cancer-special survival(BCSS).Propensity score matching(PSM)was carried out to balance cohort baselines.In addition,an exploratory analysis was performed to verify the effectiveness of radiotherapy in subgroup patients.ResultsThe median follow-up duration was 92 months.The cumulative 15-year BCSS rate for lumpectomy plus postoperative radiotherapy group,lumpectomy alone group and mastectomy alone group were 94.39%,91.51% and 92.19%,respectively(P < 0.001).The adjusted hazard ratio(HR)of BCSS was 0.63(95%CI,0.49 to 0.83;P = 0.001)for lumpectomy plus postoperative radiotherapy group versus lumpectomy alone group.After PSM,similar results were yielded(HR=0.66;95%CI,0.48-0.92;P = 0.015).The benefit of radiotherapy was well consistent across all subgroups for those who underwent lumpectomy.The adjusted HR of BCSS was 0.72(95%CI,0.56-0.92;P =0.009)for lumpectomy plus postoperative radiotherapy group versus mastectomy alone group.After PSM,results did not change substantially(HR=0.62;95%CI,0.46-0.83;P = 0.001).There was no significant difference in BCSS between lumpectomy alone group and mastectomy alone group.ConclusionAmong women with T1-2N0M0(tumor size ? 3cm)PMBC,the addition of radiotherapy after lumpectomy was significantly associated with BCSS benefit compared with lumpectomy alone or mastectomy alone.Furthermore,our research may not also provide novel evidence for precision medicine in women with early PMBC,but also reveal that the effect of radiotherapy on prognosis may result from the dual effects on the local and systemic controls.